JP7070421B2 - Electrode with heat-resistant insulating layer - Google Patents

Description

The present invention relates to electrodes, batteries, manufacturing methods thereof, and vehicles equipped with the batteries.

In a high energy density battery, the amount of heat generated becomes large when a metal foreign substance is mixed in and a short circuit occurs in the battery for some reason. For the purpose of ensuring the safety of the battery during such heat generation, an insulating coating technique for coating the electrode surface mainly with inorganic particles is known.

Patent Document 1 describes a porous insulating layer containing insulating inorganic particles and a resin for binding the particles on the positive electrode mixture layer or the negative electrode mixture layer. By providing such an insulating layer, even if at least a part of the separator between the positive electrode mixture layer and the negative electrode mixture layer disappears due to heat shrinkage or melting, the positive electrode is used by utilizing the porous insulating layer. It is possible to avoid a situation in which the mixture layer and the negative electrode mixture layer are short-circuited. The insulating layer is formed by applying a coating agent to the positive electrode mixture layer or the negative electrode mixture layer.

Japanese Unexamined Patent Publication No. 2010-282849

When the amount of heat generated is large, an insulating layer using a resin having higher heat resistance is required. Polyimide is mentioned as a resin having high heat resistance. Polyimide has poor plasticity due to its heat resistance. Generally, the varnish of polyamic acid, which is a precursor thereof, is first formed on a film or coating film, and then exposed to a high temperature of over 300 ° C. to form polyamic acid. Is reacted (imidized) with polyimide to finally obtain a polyimide resin-formed body having excellent heat resistance and strength.

However, when the above-mentioned method for producing a polyimide-forming body is applied to the binder for the insulating layer described in Patent Document 1, there is a problem that the electrode needs to be heat-treated at a temperature of 300 ° C. or higher together with the insulating layer. The heat treatment of the electrode at a high temperature may cause oxidation of the current collector, melting of the binder used for the electrode mixture layer, and thermal deterioration. Oxidation of the current collector results in a decrease in the adhesive strength between the electrode mixture layer and the current collector. Melting and thermal deterioration of the binder result in closing the voids of the electrode mixture layer and impairing the binding property of the active material particles. These cause deterioration of battery characteristics, especially shortening of life.

In view of the above-mentioned problems, an object of the present invention is to provide an electrode in which thermal deterioration is suppressed even though it has an insulating layer containing polyimide.

The present invention relates to an electrode having a current collector and an electrode mixture layer, and having an insulating layer containing an aromatic compound having an electron donating group and an organic acid group and a polyimide.

According to the present invention, it is possible to provide an electrode in which deterioration due to heat is suppressed even though it has an insulating layer containing polyimide.

It is an exploded perspective view which shows the basic structure of a film exterior battery. It is sectional drawing which shows typically the cross section of the battery of FIG.

1. 1. Electrode The electrode has an insulating layer. Other configurations may be the same as known configurations. In addition to the insulating layer, the electrode includes an electrode mixture layer containing a binder and an active material, and a current collector. The electrode according to this embodiment may be used as a positive electrode or a negative electrode.

[Insulation layer]
The insulating layer is one that is applied or adhered to the electrode and integrated with the electrode. The insulating layer is provided, for example, on the electrode mixture layer or the portion of the current collector to which the electrode mixture layer is not applied. By providing the insulating layer in such a place, it is possible to prevent the electrode mixture layer or the current collector of the positive electrode and the electrode mixture layer or the current collector of the negative electrode from coming into contact with each other.

The insulating layer contains polyimide. Unless otherwise specified, the "polyimide" described herein may include polyamide-imide as well as polyimide.

Polyimide (excluding polyamide-imide in this case) is a polymer containing at least a part of the repeating unit represented by the following formula (1).

（式（１）中、Ａはテトラカルボン酸二無水物から酸無水物基を除いた４価の基であり、Ｂはジアミンからアミノ基を除いた２価の基である。）

(In the formula (1), A is a tetravalent group obtained by removing an acid anhydride group from a tetracarboxylic acid dianhydride, and B is a divalent group obtained by removing an amino group from a diamine.)

Tetracarboxylic acid dianhydride and diamine are commonly used as raw materials for polyimide. Tetracarboxylic acid dianhydride and diamine are condensed to form an imide group contained in the formula (1).

The structure of the polyimide used for the insulating layer is not particularly limited, and a commercially available polyimide may be used. In the formula (1), examples of the tetracarboxylic acid dianhydride forming A include 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 3,4'. -Aromatic tetracarboxylic acid dianhydrides such as oxydiphthalic acid anhydrides, 4,4'-oxydiphthalic acid anhydrides, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydrides, and cyclobutanetetracarboxylic acid dianides. Anhydrous, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3 Examples thereof include aliphatic tetracarboxylic acid dianhydrides such as 5,6-tetracarboxylic acid dianhydride and 1,2,3,4-butanetetracarboxylic acid dianhydride. In the formula (1), examples of the diamine forming B include aromatic diamines such as p-phenylenediamine, m-phenylenediamine, p-xylylenediamine and m-xylylenediamine, and cyclohexanediamine and di (amino). Examples thereof include aliphatic diamines such as methyl) cyclohexane, diaminomethylbicycloheptane, and diaminomethyloxybicycloheptane.

Polyamideimide is a polymer containing at least a part of the repeating unit represented by the following formula (1)'.

（式（１）’中、Ａはトリカルボン酸無水物からカルボン酸基および酸無水物基を除いた３価の基であり、Ｂはジアミンからアミノ基を除いた２価の基である。）

(In the formula (1)', A is a trivalent group obtained by removing a carboxylic acid group and an acid anhydride group from a tricarboxylic acid anhydride, and B is a divalent group obtained by removing an amino group from a diamine.)

The structure of the polyamide-imide used for the insulating layer is not particularly limited, and may be a commercially available polyamide-imide. In the formula (1)', examples of the tricarboxylic acid anhydride forming A include trimellitic acid anhydride, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydrous, 3,4,4'. -Biphenyltricarboxylic acid anhydride, 3,4,4'-diphenylmethanetricarboxylic acid anhydride and the like can be mentioned. In the formula (1)', examples of the diamine forming B include the diamine exemplified in the formula (1).

The polyimide may contain both the repeating units of the formulas (1) and (1)'.

The polyimide may partially contain a repeating unit of the polyamic acid represented by the precursor formula (2) or (2)'.

（式（２）中、ＡおよびＢは、式（１）におけるＡおよびＢとそれぞれ同一の意味である。）

(In the formula (2), A and B have the same meaning as A and B in the formula (1), respectively.)

（式（２）’中、ＡおよびＢは、式（１）’におけるＡおよびＢとそれぞれ同一の意味である。）

(In equation (2)', A and B have the same meaning as A and B in equation (1)', respectively.)

In polyimide, it is represented by the formula (1) or (1)'for the total number of repeating units represented by the formula (1) or (1)'and the repeating unit represented by the formula (2) or (2)'. The ratio of the total number of repeating units (hereinafter, also referred to as imidization rate) is not particularly limited and may be appropriately set by those skilled in the art. The imidization ratio can be adjusted by adjusting the temperature of the heat treatment for reacting the polyamic acid with the polyimide. The imidization ratio may be, for example, 50% or more, 80% or more, or 100%. The imidization rate of the polyamic acid can be determined by using NMR or FTIR.

The content of the repeating unit represented by the above formula (1) or (1)'in the polyimide is not particularly limited and is appropriately determined. For example, it may be 50 mol% or more, 80 mol% or more, or 100 mol% or more of all repetition units.

The content of polyimide in the insulating layer is not particularly limited and may be appropriately set by those skilled in the art. The content of polyimide in the insulating layer depends on the content of other additives, particularly the insulating filler described below. If the insulating layer does not contain an insulating filler, the polyimide may be the main material of the insulating layer. The polyimide content may be, for example, 50% by mass or more or 80% by mass or more of the insulating layer as the lower limit, and 99.9% by mass or less or 95% by mass or less of the insulating layer as the upper limit. When the insulating filler is contained, the insulating layer may be mainly composed of the insulating filler, and polyimide is mainly added to bind the insulating filler. The polyimide content may be, for example, 0.5% by mass or more or 1% by mass or more of the insulating layer as the lower limit, and 90% by mass or less, 70% by mass or less, or 50% by mass or less of the insulating layer as the upper limit. It's okay.

The insulating layer contains a catalyst that promotes imidization at low temperatures. The catalyst is preferably an aromatic compound having an electron donating group and an organic acid group (hereinafter, also simply referred to as "aromatic compound"). Aromatic compounds with only organic acid groups have also been reported to promote imidization. However, when an aromatic compound having an electron donating group and an organic acid group is used, a high imidization rate can be obtained even by heat treatment at a lower temperature. In the heat treatment, the current collector and the electrode mixture layer are heated together with the insulating layer, but by lowering the temperature of the heat treatment, the current collector is oxidized, the binder used for the electrode mixture layer is melted, and the binder is melted. Thermal deterioration can be prevented.

The electron-donating group may be a group in which the substituent constant of Hammett's rule becomes negative when substituted with the para-position of benzoic acid. For example, examples of the electron donating group include an alkyl group, an alkoxy group, an amino group, a hydroxyl group, a mercapto group, and an alkylthio group. Among these, an alkyl group and a hydroxyl group are particularly preferable, and a hydroxyl group is the most preferable. The number of electron donating groups present in the aromatic compound may be one or more. Preferably, the number of electron donating groups is one. The number of carbon atoms of the alkyl group, the alkoxy group, and the alkylthio group is not particularly limited, but may be, for example, 1 to 4.

Examples of the organic acid group include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. Of these, the carboxylic acid group is particularly preferable. The number of organic acid groups present in the aromatic compound may be one or more, but is preferably one or two, and most preferably one. If an excessive organic acid group is present in the aromatic compound, it may react three-dimensionally with the polyamic acid to form a gel. In order to prevent this, it is preferable that the number of organic acid groups is 2 or less in the aromatic compound. When two or more organic acid groups are present in the aromatic compound, the organic acid groups are preferably arranged at positions separated from each other, such as the para position and the meta position in the case of a benzene ring. By arranging the organic acid groups at positions separated from each other, it is possible to prevent the organic acid groups of the aromatic compound from condensing in the molecule.

The aromatic compound is preferably one in which hydrogen on the aromatic ring is directly substituted with an electron donating group and an organic acid group. Examples of the skeleton of the aromatic compound include benzene, biphenyl, naphthalene and the like. Among these, benzene having a low molecular weight is particularly preferable in order to improve the energy density of the battery.

Preferred aromatic compounds include hydroxy benzoic acid, amino benzoic acid, alkyl benzoic acid, mercapto benzoic acid, alkoxy benzoic acid, alkylthio benzoic acid, hydroxybiphenyl carboxylic acid, aminobiphenyl carboxylic acid, alkyl biphenyl carboxylic acid, mercapto biphenyl carboxylic acid. , Alkoxybiphenylcarboxylic acid, alkylthiobiphenylcarboxylic acid, hydroxynaphthalenecarboxylic acid, aminonaphthalenecarboxylic acid, alkylnaphthalenecarboxylic acid, mercaptonaphthalenecarboxylic acid, alkoxynaphthalenecarboxylic acid, alkylthionaphthalenecarboxylic acid and the like. In these compounds, the substitution positions of the electron donating group and the organic acid group are not particularly limited, but a compound in which the electron donating group and the organic acid group are substituted apart is more preferable. When the skeleton of the aromatic compound is benzene, a compound in which the electron donating group and the organic acid group are substituted at the meta-position or the para-position, particularly the para-position is preferable. When the skeleton of the aromatic compound is biphenyl, the compound in which the electron donating group and the organic acid group are substituted at the 4,4'-position, 3,4'-position or 3,3'-position, particularly the 4,4'-position. Is preferable. When the skeleton of the aromatic compound is naphthalene, compounds in which the electron donating group and the organic acid group are substituted at the 2,6, 2,7 or 2,4 positions, particularly the 2,6 position are preferable.

Aromatic compounds are used to react the precursor polyamic acid with polyimide at lower temperatures. After the reaction, at least some aromatic compounds retain their structure and remain in the insulating layer. The content of the aromatic compound in the insulating layer is preferably 60% by mass or less, more preferably 40% by mass or less as an upper limit, and preferably 0.01% by mass as a lower limit with respect to the polyimide contained in the insulating layer. As mentioned above, it is more preferably 3% by mass or more.

The insulating layer may further contain an insulating filler as an optional component. Examples of the insulating filler include metal oxides and nitrides, specifically, aluminum oxide (alumina), silicon oxide (silica), titanium oxide (titania), zirconium oxide (zirconia), and magnesium oxide (magnesia). , Inorganic particles such as zinc oxide, strontium titanate, barium titanate, aluminum nitride, silicon nitride, and organic particles such as silicone rubber.

The content of the insulating filler in the insulating layer is not particularly limited and may be appropriately set by those skilled in the art. When the insulating filler is added, the content of the insulating filler is preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 50% by mass or more of the insulating layer as the lower limit. The upper limit is preferably 99.5% by mass or less of the insulating layer, and more preferably 99% by mass or less.

The particle size of the insulating filler is not particularly limited and may be appropriately set by those skilled in the art. The 50% particle size (D50) of the insulating filler is preferably 0.1 μm or more, more preferably 0.3 μm or more as the lower limit, preferably 10.0 μm or less, and more preferably 1.0 μm or less as the upper limit. Is. The 50% particle size (D50) can be measured by a laser diffraction particle size distribution measuring device (volume basis).

When the insulating layer is provided on the electrode mixture layer, the insulating layer preferably has holes for allowing ions to pass therethrough. The porosity of the insulating layer is not particularly limited and may be appropriately set by those skilled in the art. The porosity is preferably 30% or more as the lower limit, more preferably 40% or more, and the upper limit is preferably 90% or less, more preferably 80% or less. The porosity of the insulating layer is measured by the mercury intrusion method.

The electrode having an insulating layer can be manufactured by a known method. In one embodiment, the method for producing an electrode having an insulating layer is a step of applying a polyamic acid solution containing a polyamic acid, an aromatic compound having an electron donating group and an organic acid group, and a solvent to the electrode, and heat treatment of the electrode. Including the process of

The solvent used for the polyamic acid solution may be appropriately selected by those skilled in the art. For example, as a solvent, N-methyl-2-pyrrolidone (abbreviation: NMP), N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazole Ridineon and the like can be mentioned.

By including the aromatic compound in the polyamic acid solution, a high imidization rate can be achieved even at a lower temperature. In the polyamic acid solution, the aromatic compound is contained in an amount of preferably 60% by mass or less, more preferably 40% by mass or less, based on the polyamic acid. Further, in the polyamic acid solution, the aromatic compound is contained in an amount of preferably 0.01% by mass or more, more preferably 3% by mass or more, based on the polyamic acid.

The polyamic acid solution may further contain other components such as a phase separator and an insulating filler. At this time, the mixture may be a slurry. If necessary, the above-mentioned method for producing an insulating layer may further include a step of forming holes in the polyamic acid layer or the polyimide layer. Examples of the method for forming the pores include known methods such as a phase separation method and an extraction method. A simple method is also known in which pores can be formed at the same time as heat treatment without providing an additional step.

For example, when a poor solvent of polyamic acid having a higher boiling point than the solvent, such as an ether solvent, is added to the polyamic acid solution as a phase separator, the solvent volatilizes during the heat treatment and the concentration of the poor solvent increases. , The poor solvent and the polyamic acid can be phase-separated to form voids in the polyamic acid layer.

For example, when a polyamic acid solution containing an insulating filler is used, the polyamic acid layer is heat-treated to form a layer of a polyimide-bound insulating filler having pores. In this method, a small amount of polyamic acid is preferably used for the insulating filler so that the polyimide acting as a binder for the insulating filler does not fill the voids.

The temperature of the heat treatment is not particularly limited and may be appropriately set by those skilled in the art. In order to prevent deterioration of the current collector and the electrode mixture layer that are heat-treated together with the insulating layer, the heat treatment temperature is preferably less than 200 ° C., more preferably 180 ° C. or lower, very preferably 150 ° C. or lower, and most preferably 130 ° C. It is below ° C. Further, in order to improve the imidization rate, the heat treatment temperature is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, and most preferably 90 ° C. or higher. The heat treatment can be carried out under any atmosphere of an inert gas such as air and nitrogen and a vacuum. The heat treatment time is preferably 1 minute or more and 24 hours or less, and more preferably 5 minutes or more and 5 hours or less, although it depends on the temperature and amount. The heat treatment may remove volatile components such as solvents in the polyamic acid solution.

[Active substance]
The positive electrode active material is not particularly limited and can be selected from several viewpoints. From the viewpoint of increasing the energy density, it is preferable to contain a high-capacity compound. Examples of the high-capacity compound include lithium nickelate (LiNiO ₂ ) or a lithium-nickel composite oxide obtained by substituting a part of Ni of lithium nickelate with another metal element, and the layered form represented by the following formula (3). Lithium-nickel composite oxides are preferred.

Li _y Ni _(1-x) M _x O ₂ (3)
(However, 0 ≦ x <1, 0 <y ≦ 1.2, M is at least one element selected from the group consisting of Co, Al, Mn, Fe, Ti and B.)

From the viewpoint of high capacity, the Ni content is high, that is, in the formula (3), x is preferably less than 0.5, and more preferably 0.4 or less. Examples of such a compound include Li _α Ni _β Co _γ Mn _δ O ₂ (0 <α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0). .2), Li _α Ni _β Co _γ Al _δ O ₂ (0 <α ≦ 1.2 preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6 preferably β ≧ 0.7, γ ≤0.2), and in particular, LiNi _β Co _γ Mn _δ O ₂ (0.75 ≤ β ≤ 0.85, 0.05 ≤ γ ≤ 0.15, 0.10 ≤ δ ≤ 0.20). ). More specifically, for example, LiNi _0.8 Co _0.05 Mn _0.15 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 . O ₂ , LiNi _0.8 Co _0.1 Al _0.1 O ₂ and the like can be preferably used.

Further, from the viewpoint of thermal stability, it is also preferable that the Ni content does not exceed 0.5, that is, x is 0.5 or more in the formula (3). It is also preferable that the specific transition metal does not exceed half. Examples of such a compound include Li _α Ni _β Co _γ Mn _δ O ₂ (0 <α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, 0.2 ≦ β ≦ 0.5, 0. .1 ≦ γ ≦ 0.4, 0.1 ≦ δ ≦ 0.4). More specifically, LiNi _0.4 Co _0.3 Mn _0.3 O ₂ (abbreviated as NCM433), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn. _0.3 O ₂ (abbreviated as NCM523), LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (abbreviated as NCM532), etc. (However, the content of each transition metal in these compounds varies by about 10%. (Including those that have been used).

Further, two or more compounds represented by the formula (3) may be mixed and used, and for example, NCM532 or NCM523 and NCM433 may be used in the range of 9: 1 to 1: 9 (typically, 2). It is also preferable to mix and use in 1). Further, a material having a high Ni content (x is 0.4 or less) in the formula (3) and a material having a Ni content not exceeding 0.5 (x is 0.5 or more, for example, NCM433) are mixed. By doing so, it is possible to construct a battery having a high capacity and high thermal stability.

In addition to the above, as positive electrode active materials, for example, LiMnO ₂ , Li _x Mn ₂ O ₄ (0 <x <2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0 <x <). Lithium manganate having a layered structure or spinel structure such as 2); LiCoO ₂ or a part of these transition metals replaced with another metal; Excessive ones; and those having an olivine structure such as LiFePO ₄ can be mentioned. Further, a material in which these metal oxides are partially replaced with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La and the like. Can also be used. Any of the positive electrode active materials described above can be used alone or in combination of two or more.

The negative electrode active material is not particularly limited, and specific examples thereof include metals, metal oxides, and carbon.

Examples of the metal include Li, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, or alloys of two or more of these. .. In addition, two or more of these metals or alloys may be mixed and used. Further, these metals or alloys may contain one or more non-metal elements.

Examples of the metal oxide include silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, and a composite thereof. In the present embodiment, the negative electrode active material of the metal oxide preferably contains tin oxide or silicon oxide, and more preferably silicon oxide. This is because silicon oxide is relatively stable and does not easily cause a reaction with other compounds. As the silicon oxide, those represented by the composition formula SiO _x (where 0 <x ≦ 2) are preferable. Further, for example, 0.1 to 5% by mass of one or more elements selected from nitrogen, boron and sulfur can be added to the metal oxide. By doing so, the electrical conductivity of the metal oxide can be improved.

Examples of carbon include graphite, amorphous carbon, graphene, diamond-like carbon, carbon nanotubes, and composites thereof. Here, graphite having high crystallinity has high electrical conductivity, and is excellent in adhesiveness to a negative electrode current collector made of a metal such as copper and voltage flatness. On the other hand, amorphous carbon having low crystallinity has a relatively small volume expansion, so that it has a high effect of alleviating the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as grain boundaries and defects is unlikely to occur.

Along with the active material, a conductive auxiliary material may be added to the electrode mixture layer for the purpose of lowering the impedance. Examples of the conductive auxiliary material include scaly, soot-like, and fibrous carbonaceous fine particles, such as graphite, carbon black, acetylene black, and vapor phase carbon fiber (for example, VGCF manufactured by Showa Denko).

[Binder]
The binder used in the electrode mixture layer is not particularly limited. Examples of the binder include fluorinated resins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and polytetrafluoroethylene; and polyolefin resins such as polypropylene and polyethylene; Acrylics such as polyacrylic acid, polyacrylic acid salt, polymethacrylic acid, polymethacrylic acid salt, polyacrylic acid ester, polymethacrylic acid ester, copolymers composed of the monomer units constituting these resins, and cross-linked products thereof. Resin; Copolymers composed of polystyrene, polyacrylic nitrile, polybutadiene, and monomer units constituting these resins, and diene rubbers such as styrene butadiene rubber (SBR) which is a crosslinked product thereof can be used. Further, a mixture of the above-mentioned plurality of resins, a copolymer composed of monomer units constituting these resins, a crosslinked product thereof, and the like can be used. Furthermore, when an aqueous binder such as an SBR emulsion is used, a thickener such as carboxymethyl cellulose (CMC) can also be used. Polyimide and polyamide-imide can also be used. Aromatic imides are preferred. When a resin that requires heat treatment (imidization reaction) at a high temperature is used among these, an aromatic compound having an electron donating group and an organic acid group exemplified as an imidization catalyst of the insulating layer is used in combination with polyimide. Is preferable.

In one embodiment, as the resin used as the binder for the electrode mixture layer, a highly rubbery material capable of firmly binding the active material with a small amount is preferable from the viewpoint of battery life. In general, such resins often have low heat resistance. That is, the melting point or heat resistant temperature of the binder is preferably 200 ° C. or lower, more preferably 170 ° C. or lower. On the other hand, a binder having excessively low heat resistance may interfere with the function as a battery, and the melting point or heat resistant temperature of the binder is preferably 80 ° C. or higher, more preferably 100 ° C. or higher. More specifically, such a binder includes polyvinylidene fluoride, polypropylene, polyethylene, styrene butadiene rubber, polyacrylic acid, polyacrylic acid salt, polymethacrylic acid, polymethacrylic acid salt, polyacrylic acid ester, and polymethacrylic acid. Examples include acid esters. The melting point of the resin can be determined, for example, by the melting temperature measured using a differential scanning calorimeter (DSC) according to JIS K7121.

A plurality of binders may be mixed and used. The amount of the binder to be used is preferably 2 to 20 parts by mass with respect to 100 parts by mass of the active material from the viewpoint of "sufficient binding force" and "high energy" which are in a trade-off relationship.

[Current collector]
The current collector is not particularly limited. Aluminum, nickel, stainless steel, chromium, copper, silver, and alloys thereof can be used as the negative electrode current collector because of its electrochemical stability. As the positive electrode current collector, aluminum, nickel, silver, or an alloy thereof can be used. Examples of the shape of the current collector include a foil, a flat plate, and a mesh.

2. 2. An electrode having a battery insulating layer can be used for at least one of a positive electrode and a negative electrode to produce a highly safe battery. Batteries can be made according to conventional methods. An example of a method for manufacturing a battery will be described by taking a laminated laminated battery as an example. First, in dry air or an inert atmosphere, the positive electrode and the negative electrode are arranged so as to face each other with the separator interposed therebetween to form an electrode element. Next, this electrode element is housed in an exterior body (container), and an electrolytic solution is injected to impregnate the electrode with the electrolytic solution. After that, the opening of the exterior body is sealed to complete the battery. Hereinafter, embodiments of configurations other than the electrodes will be described.

[Separator]
By using an electrode having an insulating layer on at least one of a positive electrode and a negative electrode, the battery does not have to be provided with a separator. In this case, the raw material cost and the manufacturing cost of the battery can be reduced. The insulating layer may be used with the separator. In this case, even if the separator melts or shrinks during heat generation, the insulating layer can maintain the insulation between the positive electrode and the negative electrode.

The separator may be any as long as it suppresses the conduction between the positive electrode and the negative electrode without inhibiting the permeation of the charged body and has durability against the electrolytic solution. Specific materials include polyolefins such as polypropylene and polyethylene, polyesters such as cellulose, polyethylene terephthalate and polybutylene terephthalate, polyimide, polyvinylidene fluoride and polymethaphenylene isophthalamide, polyparaphenylene terephthalamide and copolyparaphenylene-3, Examples thereof include aromatic polyamides (aramid) such as 4'-oxydiphenylene terephthalamide. These can be used as porous films, woven fabrics, non-woven fabrics and the like.

[Electrolytic solution]
The electrolytic solution is not particularly limited, but a non-aqueous electrolytic solution containing a non-aqueous solvent and a supporting salt that is stable at the action potential of the battery is preferable.

Examples of non-aqueous solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC); dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. Chain carbonates such as dipropyl carbonate (DPC); propylene carbonate derivatives; aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate; ethers such as diethyl ether and ethyl propyl ether, trimethyl phosphate, Aprotonic organic solvents such as phosphate esters such as triethyl phosphate, tripropyl phosphate, trioctyl phosphate, and triphenyl phosphate, and fluorine in which at least a part of the hydrogen atom of these compounds is replaced with a fluorine atom. Examples thereof include chemical aproton organic solvents.

Among these, cyclics such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), and dipropyl carbonate (DPC). Alternatively, it is preferable to contain chain carbonates.

The non-aqueous solvent may be used alone or in combination of two or more.

Supporting salts include LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN ₍ CF ₃ SO). ) _2nd class lithium salt can be mentioned. The supporting salt can be used alone or in combination of two or more. LiPF ₆ is preferable from the viewpoint of cost reduction.

[Battery structure]
The battery of the present embodiment has, for example, the structures shown in FIGS. 1 and 2. This battery includes a battery element 20, a film exterior 10 that houses the battery element 20 together with an electrolyte, and a positive electrode tab 51 and a negative electrode tab 52 (hereinafter, these are also simply referred to as “electrode tabs”).

As shown in FIG. 2, the battery element 20 is formed by alternately stacking a plurality of positive electrodes 30 and a plurality of negative electrodes 40 with a separator 25 interposed therebetween. The positive electrode 30 has the electrode material 32 coated on both sides of the metal foil 31, and the negative electrode 40 also has the electrode material 42 coated on both sides of the metal foil 41. It should be noted that the present invention can be applied not only to a laminated type battery but also to a wound type battery and the like.

The battery to which the present invention can be applied may have a configuration in which the electrode tabs are pulled out to one side of the exterior body as shown in FIGS. 1 and 2, but the battery has electrode tabs drawn out to both sides of the exterior body. There may be. Although detailed illustration is omitted, the metal foils of the positive electrode and the negative electrode each have an extension portion on a part of the outer circumference. The extension of the negative electrode metal leaf is collected together and connected to the negative electrode tab 52, and the extension of the positive electrode metal leaf is collected and connected to the positive electrode tab 51 (see FIG. 2). The portions gathered together in the stacking direction between the extension portions in this way are also called "current collectors".

In this example, the film exterior body 10 is composed of two films 10-1 and 10-2. The films 10-1 and 10-2 are heat-sealed to each other at the peripheral portion of the battery element 20 and sealed. In FIG. 1, the positive electrode tab 51 and the negative electrode tab 52 are pulled out in the same direction from one short side of the film exterior body 10 sealed in this way.

Of course, the electrode tabs may be pulled out from two different sides. Regarding the composition of the film, FIGS. 1 and 2 show an example in which the cup portion is formed on one film 10-1 and the cup portion is not formed on the other film 10-2. In addition to this, a configuration in which a cup portion is formed on both films (not shown), a configuration in which both films do not form a cup portion (not shown), and the like can be adopted.

3. 3. Assembled battery A plurality of batteries according to the present embodiment can be combined to form an assembled battery. As the assembled battery, for example, two or more batteries according to the present embodiment may be used and connected in series, in parallel, or both. By connecting in series and / or in parallel, the capacity and voltage can be freely adjusted. The number of batteries included in the assembled battery can be appropriately set according to the battery capacity and output.

4. Vehicle The battery or the assembled battery thereof according to the present embodiment can be used in a vehicle. Vehicles according to this embodiment include hybrid vehicles, fuel cell vehicles, electric vehicles (all are four-wheeled vehicles (passenger vehicles, trucks, commercial vehicles such as buses, light vehicles, etc.), as well as two-wheeled vehicles (motorcycles) and three-wheeled vehicles. ). The vehicle according to the present embodiment is not limited to an automobile, and can be used as various power sources for other vehicles, for example, moving objects such as trains.

The positive electrode C-1 was obtained as follows. LiNi _0.80 Co _0.15 Al _0.05 O ₂ (hereinafter also referred to as NCA), which is a layered lithium nickel composite oxide as a positive electrode active material, carbon black as a conductive auxiliary material, and polyvinylidene fluoride as a binder. Vinylidene fluoride (hereinafter, also referred to as PVdF) was weighed at a mass ratio of 90: 5: 5, and they were kneaded with N-methylpyrrolidone to obtain a positive electrode slurry. The prepared positive electrode slurry was applied to an aluminum foil having a thickness of 20 μm as a current collector with a doctor blade, heated and dried at 110 ° C. for 5 minutes, and further pressed to obtain a positive electrode C-1.

Four types of negative electrodes A-1 to 4 were obtained as follows.

(Negative electrode A-1)
Artificial graphite (hereinafter also referred to as C) and an aqueous solution of carboxymethyl cellulose (CMC) are kneaded using a rotation / revolution mixer (Awatori Rentaro ARE-500 manufactured by Shinky Co., Ltd.), and then a styrene-butadiene copolymer (SBR) is used. Was added to prepare a negative electrode slurry. The mass ratio of artificial graphite, CMC and SBR was 97: 1: 2. This slurry was applied onto a copper foil having a thickness of 10 μm with a doctor blade, dried by heating at 110 ° C. for 5 minutes, and further pressed to prepare a negative electrode A-1.

(Negative electrode A-2)
Artificial graphite, polyvinylidene fluoride resin (PVdF) and N-methylpyrrolidone were kneaded using a rotation / revolution mixer (Awatori Rentaro ARE-500 manufactured by Shinky Co., Ltd.) to prepare a negative electrode slurry. The mass ratio of artificial graphite to PVdF was 95: 5. This slurry was applied onto a copper foil having a thickness of 10 μm with a doctor blade, dried by heating at 110 ° C. for 5 minutes, and further pressed to prepare a negative electrode A-2.

(Negative electrode A-3)
A composite (hereinafter also referred to as SiO) in which the surface of SiO _x having a 50% particle diameter of 8 μm is coated with a carbon material (the amount of carbon material in the composite was 7% by mass) and a polyamic acid solution (hereinafter also referred to as SiO) and a polyamic acid solution (hereinafter referred to as SiO). Product name: "U-Wanis A", manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass) and p-hydroxybenzoic acid were weighed at a mass ratio of 50:49:0.5, respectively. These were kneaded with n-methylpyrrolidone to prepare a slurry. The slurry was applied onto a copper foil having a thickness of 10 μm using a doctor blade. Then, it was heated at 120 ° C. for 5 minutes to dry n-methylpyrrolidone. After pressing this, it was heated at 150 ° C. for 1 hour under normal pressure in air to obtain a negative electrode A-3.

(Negative electrode A-4)
A composite having a 50% particle size of 8 μm and a surface coated with a carbon material (the amount of the carbon material in the composite was 7% by mass) and a polyamic acid solution (trade name: “U- _Wanis A”). , Ube Kosan Co., Ltd., polyamic acid 20% by mass) were weighed at a mass ratio of 50:49, respectively. These were kneaded with n-methylpyrrolidone to prepare a slurry. The slurry was applied onto a copper foil having a thickness of 10 μm using a doctor blade. Then, it was heated at 120 ° C. for 5 minutes to dry n-methylpyrrolidone. After pressing this, it was heated at 350 ° C. for 1 hour under normal pressure in air to obtain a negative electrode A-4.

Nine kinds of insulating layer slurries I-1 to 9 were obtained as follows.

(Insulation layer slurry I-1)
Alumina particles (50% particle diameter 1.0 μm) and n-methylpyrrolidone solution of polyamic acid as a binder (trade name: “U-Wanis A”, manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass). , P-Hydroxybenzoic acid was weighed at a mass ratio of 90: 10: 0.1, respectively. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-1.

(Insulation layer slurry I-2)
Alumina particles (50% particle diameter 1.0 μm) and n-methylpyrrolidone solution of polyamic acid as a binder (trade name: “U-varnish A”, manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass). , P-Methylbenzoic acid was weighed at a mass ratio of 90: 10: 0.1, respectively. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-2.

(Insulation layer slurry I-3)
Alumina particles (50% particle diameter 1.0 μm) and n-methylpyrrolidone solution of polyamic acid as a binder (trade name: “U-varnish A”, manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass). , M-Hydroxybenzoic acid was weighed at a mass ratio of 90: 10: 0.1, respectively. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-3.

(Insulation layer slurry I-4)
Alumina particles (50% particle diameter 1.0 μm) and n-methylpyrrolidone solution of polyamic acid as a binder (trade name: “U-Wanis A”, manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass). , O-Hydroxybenzoic acid was weighed at a mass ratio of 90: 10: 0.1, respectively. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-4.

(Insulation layer slurry I-5)
Alumina particles (50% particle diameter 1.0 μm) and n-methylpyrrolidone solution of polyamic acid as a binder (trade name: “U-varnish A”, manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass). Weighed at a mass ratio of 90:10, respectively. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-5.

(Insulation layer slurry I-6)
An n-methylpyrrolidone solution of polyamic acid (trade name: "U-varnish A", manufactured by Ube Kosan Co., Ltd.) was concentrated to adjust the solid content concentration to 50% by mass. This concentrated solution, triethylene glycol dimethyl ether, and p-hydroxybenzoic acid were weighed at a mass ratio of 10:20:0.25, respectively. This was mixed to obtain an insulating layer slurry I-6. Although this mixture is a solution, it is referred to as an insulating layer slurry I-6 for convenience.

(Insulation layer slurry I-7)
An n-methylpyrrolidone solution of polyamic acid (trade name: "U-varnish A", manufactured by Ube Kosan Co., Ltd.) was concentrated to adjust the solid content concentration to 50% by mass. The concentrated solution and triethylene glycol dimethyl ether were weighed in a mass ratio of 10:20, respectively. This was mixed to obtain an insulating layer slurry I-7. Although this mixture is a solution, it is referred to as an insulating layer slurry I-7 for convenience.

(Insulation layer slurry I-8)
Trimellitic acid chloride and diaminodiphenylmethane were stirred and mixed in an n-methylpyrrolidone solution to obtain an n-methylpyrrolidone solution (polymer concentration 20% by mass) of polyamic acid as a polyamide-imide precursor. The number average molecular weight of the polyamic acid was 41000. Alumina particles (50% particle diameter 1.0 μm), n-methylpyrrolidone solution of polyamic acid prepared as a binder, and p-hydroxybenzoic acid are weighed at a mass ratio of 90: 10: 0.1, respectively. bottom. These were kneaded with n-methylpyrrolidone to obtain an insulating layer slurry I-8.

(Insulation layer slurry I-9)
The insulating layer slurry I-9 obtained in the same manner as the insulating layer slurry I-8 except that p-hydroxybenzoic acid was not added was used as the insulating layer slurry I-9.

The insulating layer slurries I-1 to 9 are applied to the surface of the electrodes (positive electrode C-1 or negative electrodes A-1 to 4) shown in Table 1 with a doctor blade and heated at 120 ° C. for 5 minutes to dry n-methylpyrrolidone. I let you. After pressing this, it was heated at the temperature shown in Table 1 below (150 ° C. to 350 ° C.) for 1 hour under normal pressure in air to obtain an electrode having an insulating layer. When the cross section was observed with an electron microscope, the thickness of the insulating layer was 3 to 8 μm. The ¹³ C-NMR of the insulating layer was measured, and the molar ratio of polyamic acid (carbon shown at 169 ppm), which is a component of the binder used as a raw material, and polyimide (carbon shown at 166 ppm) obtained by the ring closure reaction was determined. It was estimated by the waveform separation method, and the imidization rate was calculated based on this. Table 1 shows the results as x when the imidization rate is less than 80%, ◯ when the imidization rate is 80% or more and less than 85%, and ⊚ when the imidization rate is 85% or more.

In each example, the combination of the positive electrode and the negative electrode shown in Table 1 was used. Aluminum terminals and nickel terminals were welded to these positive and negative electrodes, respectively. These were alternately laminated via a separator to prepare an electrode element. The electrode element was exteriorized with a laminated film, and an electrolytic solution was injected into the laminated film. Then, the laminating film was heat-sealed and sealed while reducing the pressure inside the laminating film. As a result, a plurality of flat plate type secondary batteries before the first charge were produced. A single-layer polypropylene microporous membrane (thickness 20 μm) was used as the separator. As the laminated film, a polypropylene film on which aluminum was vapor-deposited was used. As the electrolytic solution, a solution containing 1.0 mol / l LiPF ₆ as an electrolyte and a mixed solvent of ethylene carbonate and diethyl carbonate (7: 3 (volume ratio)) as a non-aqueous electrolytic solvent was used.

(Battery capacity)
The prepared secondary battery was charged to 4.2 V. Charging was performed by the CCCV method using a 0.2 C current, and after reaching 4.2 V, the voltage was kept constant for 1 hour. Next, discharge was performed at 0.2 C to 2.5 V by the CC method. The discharge capacity at this time is shown in Table 1 as the initial capacity. Subsequently, this charging and discharging operation was repeated. Here, the 0.2C current means a current that takes 5 hours to be completely discharged when a battery in an arbitrary fully charged state is discharged with a constant current. In each example, charging and discharging were performed at 200 mA. Table 1 shows the ratio of the 500th discharge capacity to the initial discharge capacity as the capacity retention rate.

The catalysts A to D shown in Table 1 are the following compounds.

Catalyst A: p-hydroxybenzoic acid Catalyst B: p-methylbenzoic acid Catalyst C: m-hydroxybenzoic acid Catalyst D: o-hydroxybenzoic acid

From Examples 1 to 4 and Comparative Example 1, and Example 8 and Comparative Example 11, it is recognized that the imidization rate is improved even by the heat treatment at 150 ° C. or lower by adding the catalyst to the insulating layer. It is considered that the improvement in the strength of the insulating layer stabilizes the electrode mixture layer even if the electrode expands and contracts due to charging and discharging, so that the maintenance rate after 500 cycles is improved. In Example 5, the binder of the negative electrode mixture layer is changed from SBR to PVdF having a low heat resistance of 200 ° C. or lower, but since the heat treatment of the insulating layer is performed at 150 ° C. or lower, the initial capacity is changed. There is no effect on the capacity retention rate after 500 cycles. On the other hand, when the heat treatment temperature is raised to 180 ° C. to 200 ° C. as shown in Comparative Examples 7 to 10, the binder of the electrode mixture layer deteriorates and a part of the conductive path is lost. Is considered to have decreased.

Comparative Examples 2 to 4 are the results of raising the heat treatment temperature to 350 ° C. Although the imidization rate of the insulating layer was good, the heat treatment temperature was about 200 ° C. higher than the heat resistant temperature of the binder of the negative electrode mixture layer, so that the binding force was lost and a sufficient initial capacity was obtained. It couldn't function as a battery. Further, it was confirmed that the copper foil of the current collector was oxidatively deteriorated after the heat treatment.

In Example 6 and Comparative Example 5, in the negative electrode, SiO is used as the negative electrode active material and polyimide is used as the binder. In Example 6, since a catalyst is used for each of the polyimides used in the electrode mixture layer and the insulating layer, it functions even at a low heat treatment temperature of 150 ° C. In Comparative Example 5, no catalyst was used for any of the polyimides. Since the heat treatment temperature was set to 350 ° C., the imidization rate increased and a strong insulating layer was formed, but the capacity retention rate after 500 cycles decreased. It is presumed that the capacity retention rate decreased due to the peeling of the current collector and the electrode mixture layer. It is considered that the adhesive strength between the copper foil of the current collector whose surface was oxidized by the heat treatment at 350 ° C. and the electrode mixture layer was lowered.

In Example 7 and Comparative Example 6, an insulating layer was applied to the positive electrode. Example 7 in which a catalyst was used for polyimide had the same results as in Example 1. Comparative Example 6 in which no catalyst was used for the polyimide had the same results as Comparative Example 1.

The following reference examples show the superiority of aromatic compounds having an electron donating group and an organic acid group to aromatic compounds having only an organic acid group.

[Reference Examples 2 to 8]
(Preparation of electrodes)
A composite in which the surface of SiO _x having an average particle diameter D of 50% of 8 μm is coated with a carbon material (the amount of carbon material in the composite is 7% by mass) and a polyamic acid solution (trade name: “U-Wanis A”, Ube). (20% by mass of polyamic acid manufactured by Kosan Co., Ltd.) and the additive were weighed at a mass ratio of 50:49: x, respectively. In Reference Examples 3 to 6, x was 0.9, and in Reference Examples 2 and 7, x was 0. In Reference Example 8, x is 2.7. These were kneaded with n-methylpyrrolidone (NMP) to prepare a slurry. The amount of water in the slurry was 200 to 300 ppm. The slurry was applied onto a copper foil having a thickness of 10 μm using a doctor blade. Then, it was heated at 120 ° C. for 5 minutes to dry NMP. Then, it was heated at 150 ° C. under normal pressure in air or 125 ° C. under nitrogen gas (flow rate 70 L / min) for 1 hour. The copper foil on which this active material layer was formed was punched into a circular shape with a diameter of 12 mm to prepare an electrode.

(Battery production)
The prepared electrodes are laminated via a Li metal counter electrode and an olefin-based separator, and a model cell is used as an electrolytic solution using EC / DEC / EMC = 3/5/2 (volume ratio) containing 1 M LiPF ₆ . Made.

(Battery evaluation)
The prepared model cell was subjected to a charge / discharge test and a cycle test at 25 ° C. In the charge / discharge test, charging / discharging is performed twice in a voltage range of 0.03 to 1.0 V with a current density of 0.3 mA / cm ² , and the amount of electricity flowing from the start to the end of discharging and charging is used as the discharge capacity and the discharge capacity. The charge capacity was set to 1C, and the second charge capacity (corresponding to the amount of delithium removed from the silicon-based electrode) was set to 1C. The 1C volume per mass of the SiO _x complex in the electrode (Reference Example 1) containing no additive such as p-hydroxybenzoic acid treated at 350 ° C. for 3 hours was set to 100, and the 1C volume ratio of the electrode was determined. rice field.

In the cycle test, the model cell after the charge / discharge test is used, and after discharging to 1.0 V at 0.3 C, constant voltage discharge is performed for a total of 4 hours, and then constant current charging is performed at 0.3 C to 0.03 V. The cycle was repeated 50 times. As the capacity retention rate, the ratio of the discharge capacity after 50 cycles to the initial charge capacity (corresponding to the amount of delithium removed from the silicon-based electrode) was determined.

[Reference Example 1]
A composite in which the surface of SiO _x having an average particle diameter D of 50% of 8 μm is coated with a carbon material (the amount of carbon material in the composite is 7% by mass) and a polyamic acid solution (trade name: “U-Wanis A”, Ube). Same as Reference Example 2 except that the mass ratio of polyamic acid (20% by mass) manufactured by Kosan Co., Ltd. was 50:49 and the heat treatment conditions were nitrogen gas (flow rate 70 L / min) and 350 ° C. for 3 hours. An electrode was prepared and evaluated.

Table 2 shows the 1C capacity ratio in each example heat-treated at 150 ° C. for 1 hour under normal pressure in air, and the average value of the capacity retention rate after 50 cycles (unit:%, number of measurements 2 or more). Table 3 shows the average value (unit:%, number of measurements 2 or more) of the 1C capacity ratio in each example heat-treated at 125 ° C. for 1 hour under nitrogen gas (flow rate 70 L / min) and the capacity retention rate after 50 cycles. Shown in.

[Reference Examples 9 and 10]
We also confirmed the case where the additive was p-aminobenzoic acid. The additive is p-aminobenzoic acid, and the SiO _x surface having an average particle size D50% of 8 μm is coated with a carbon material (the amount of carbon material in the composite is 7% by mass) and a polyamic acid solution (commodity). Name: "U-Wanis A", manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass) and additive mass ratio 50:49: x, x was 0.45, 0.20. .. Others were heat-treated at 150 ° C. for 1 hour under normal pressure in air. Electrodes were prepared in the same manner as in Reference Examples 3 to 6 and evaluated in the same manner. Table 4 shows the 1C capacity ratio at this time and the average value (unit:%, number of measurements 2 or more) of the capacity retention rate after 50 cycles.

[Reference Examples 11 to 13]
When the additive was p-hydroxybenzoic acid, the effect of the amount of p-hydroxybenzoic acid added was confirmed. The additive is p-hydroxybenzoic acid, and the SiO _x surface having an average particle size D50% of 8 μm is coated with a carbon material (the amount of carbon material in the composite is 7% by mass) and a polyamic acid solution (commodity). Name: "U-Wanis A", manufactured by Ube Kosan Co., Ltd., polyamic acid 20% by mass) and additive at a mass ratio of 50:49: x, x changed from 0.9 to 0.23, 0.10. We confirmed the case of reducing it and the case of increasing x to 4.4. Others were heat-treated at 150 ° C. for 1 hour under normal pressure in air. Electrodes were prepared in the same manner as in Reference Examples 3 to 6 and evaluated in the same manner. Table 5 shows the 1C capacity ratio at this time and the average value (unit:%, number of measurements 2 or more) of the capacity retention rate after 50 cycles.

There was a correlation between the substituent of the additive benzoic acid and the capacity of the silicon electrode after 50 cycles (formula A × B in the table). That is, an electron donating group is effective for improving the capacity of the silicon electrode. This effect was effective not only in the treatment at 150 ° C. in the air but also in the treatment at 125 ° C. under nitrogen as shown in Table 3. Further, by setting the addition amount of the benzoic acid derivative within a specific range, the capacity of the silicon electrode after 50 cycles may be further improved.

[Reference Example 14]
Electrodes were prepared by the same method as in Reference Example 3 except that the additive was changed from p-hydroxybenzoic acid to benzoic acid, and the battery characteristics were evaluated. As a result, the 1C capacity ratio (A in the table) was 44, the capacity retention rate after 50 cycles at 25 ° C. (B in the table) was 135%, and A × B ÷ 100 = 59.

As shown in Reference Example 14, when there is no substituent on the aromatic ring of benzoic acid, the initial volume (A in the table) decreases, so it is preferable to have a substituent. The reason why the capacity retention rate exceeded 100% is that Li was supplied in excess of the capacity of the prototype electrode from the counter electrode Li metal containing Li in excess of the capacity of the prototype electrode during the cycle. be. Therefore, when a counter electrode containing less Li than the capacity of the electrode of the present invention is used, it is expected that the capacity retention rate will decrease.

From the above reference example, when a polyimide binder containing an aromatic compound having an electron donating group and an organic acid group is used for an electrode using silicon as an active material, it has a high capacity even if imidization is performed at a low temperature. It turns out that batteries are available.

This application claims priority on the basis of Japanese Application Japanese Patent Application No. 2016-191000 filed on September 29, 2016 and incorporates all of its disclosures herein.

Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples. Various changes that can be understood by those skilled in the art can be made within the scope of the present invention in terms of the configuration and details of the present invention.

The electrodes according to the present invention and the batteries having the electrodes can be used, for example, in all industrial fields requiring a power source, as well as in industrial fields related to the transportation, storage and supply of electrical energy. Specifically, the power source for mobile devices such as mobile phones and laptop computers; the power source for mobile / transportation media such as electric vehicles, trains, satellites, and submarines including electric vehicles, hybrid cars, electric bikes, and electrically assisted bicycles; It can be used as a backup power source for UPS and the like; a power storage facility for storing electric power generated by solar power generation, wind power generation, etc.;

10 Film exterior 20 Battery element 25 Separator 30 Positive electrode 40 Negative electrode

Claims (9)

An electrode having a current collector and an electrode mixture layer,
An electrode having an insulating layer , which is a layer of an insulating filler having holes containing an aromatic compound having an electron donating group and an organic acid group, a polyimide , and an insulating filler bonded with the polyimide. The electrode according to claim 1, wherein the organic acid group is a carboxylic acid group. The electrode according to claim 1 or 2, wherein the electron donating group is selected from the group consisting of an alkyl group, an alkoxy group, an amino group, a hydroxyl group, a mercapto group, and an alkylthio group. At least one selected from the group consisting of a polyimide composition in which the electrode mixture layer contains polyvinylidene fluoride, polypropylene, polyethylene, and styrene butadiene rubber, an acrylic resin, and an aromatic compound having an electron donating group and an organic acid group. The electrode according to any one of claims 1 to 3, which comprises a binder. The electrode according to any one of claims 1 to 4, wherein the content of the insulating filler is 30 % by mass or more of the insulating layer. A battery having the electrode according to any one of claims 1 to 5 . A vehicle equipped with the battery according to claim 6 . It comprises a step of applying a polyamic acid solution containing a polyamic acid, an aromatic compound having an electron donating group and an organic acid group, an insulating filler, and a solvent to the electrode, and a step of heat-treating the electrode at a temperature of 180 ° C. or lower. A method for manufacturing an electrode having an insulating layer , which is a layer of an insulating filler having holes containing an insulating filler bonded with polyimide . The method for manufacturing an electrode according to claim 8, wherein the content of the insulating filler is 30% by mass or more of the insulating layer.

Images